An existing evolved packet system (Evolved Packet System, EPS) wireless network architecture mainly includes:
An evolved universal terrestrial radio access network (Evolved universal terrestrial radio access network, E-UTRAN) is a network including a plurality of evolved base stations (Evolved Node B, eNodeB), and implements a wireless physical layer function, and functions of resource scheduling and wireless resource management, radio access control, and mobility management. An eNodeB is connected to a serving gateway (Serving Gateway, S-GW) by means of an S1 user plane interface S1-U, to transfer user data, and is connected to a mobility management entity (Mobility Management Entity, MME) by means of an S1 control plane interface S1-MME, to implement a radio access bearer control function and the like by using an S1 Application Protocol S1-AP protocol.
The MME is mainly responsible for all control plane functions of user session management, including non-access stratum (Non-Access Stratum) NAS signaling and security, management of a tracking area list (Tracking Area List), and selecting a packet data network gateway (Packet Data Network Gateway, P-GW) and an S-GW.
The S-GW is mainly responsible for data transmission, data forwarding, and route switching of user equipment, and serves as a local mobility anchor point when the user equipment is handed over between eNodeBs (for each user equipment, only one S-GW serves the user equipment at each moment).
The P-GW serves as an anchor point for connecting to a packet data network (Packet Data Network, PDN), and is responsible for allocating an Internet Protocol (Internet Protocol, IP) address to the user equipment, filtering a data packet for the user equipment, performing rate control, generating charging information, and the like.
The user equipment (User Equipment, UE) is connected to the EPS network and establishes a PDN connection by means of an attach procedure. In this process, the PGW allocates an IP address to the user equipment, and the user equipment is connected to an external network by means of the PDN connection and transmits data to the external network. If no data transmission is performed for a long time, the user equipment enters an idle state (Idle). In this case, user equipment context on the eNodeB is deleted, and the MME cannot exactly know an eNodeB covering the user equipment. When the EPS network receives a downlink data packet of the user, a network side needs to first page the user equipment, and after the user equipment is switched to a connected state (Connected), send the downlink data of the user to the user equipment.
To reduce power consumption of the user equipment, a power saving mode (Power Saving Mode) and a discontinuous reception mode (Discontinuous Reception, DRX) are used in the prior art. The power saving mode refers to: the user equipment enters a sleep state, and in this state, the user equipment cannot respond to paging of the network side. The discontinuous reception mode refers to: the user equipment and the network side negotiate to use a relatively long DRX cycle value, to implement power saving for the user equipment.
In the prior art, when the user equipment enters the power saving mode, the user equipment cannot respond to the paging. When the user equipment enters the discontinuous reception mode, the MME needs to know a discontinuous reception cycle value of the user equipment, so as to correctly page the user equipment. However, because if the MME is faulty, current state information of the user equipment may be lost, the MME receiving a downlink data notification message (an MME after restart or another MME) cannot correctly page the user equipment, which causes unnecessary consumption of network resources, and even cannot implement service recovery.